Fire Flea

From Wikitroid, the Metroid wiki

The Fire Flea is an insect-like creature found on the planet Zebes. These winged creatures fly throughout many places for the sole purpose of lighting what would normally be a pitch black room, with thier brightly lit abdomens. Although these creatures will cause damage when touched, the are quite neccessary to have around. For if they are killed, the room will become darker, and if they all are killed the room will become too dark to see. Increasing that danger is the fact that they are very fragile, even the slightest touch is enough to "put them out."